In a sworn declaration in Gibson’s high profile custody battle over their one-year-old daughter, Lucia, the Oscar-winner denies his ex’s allegation that he punched Grigorieva the night of the notorious Jan. 6 incident at Gibson’s Malibu home.

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The L.A. Sheriff's Department went on to investigate Grigorieva’s claim that he assaulted her that night and knocked out two of her teeth.

In the three-page document dated June 23 and posted on TMZ.com, Gibson said the argument began in the kitchen of his Malibu home, with then two-month old Lucia in a bassinet in another room.

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“Oksana and I began to argue and as our argument escalated [in] volume, I asked her to leave my house,” Gibson wrote.

The actor said after he continued to press her to leave “Oksana stormed into the room where Lucia was, grabbed her out of her bassinet and yelled at me to ‘stop yelling or you will make her into a retarded brain damaged idiot.'”

Gibson says he watched Grigorieva run into his backyard, which he described as “dimly lit at night and located in an area where coyotes are common and even mountain lions have been spotted.”

He said he began yelling at her to return because she was running past trees with low-hanging branches and thorns and he was concerned about Lucia’s safety.

Eventually, Grigorieva ran back into the house and into her son Sacha's room.

Gibson told her to give their child to him but “she kept screaming ‘No! No!’ he wrote.

“Suddenly, Oksana started swinging Lucia erratically in her arms, jerking her body from side to side to keep Lucia out of my reach,” Gibson wrote.

Gibson said he feared “shaken baby syndrome” and “slapped Oksana one time with an open hand in an attempt to bring her back to reality.”

“I did not slap her hard, I was just trying to shock her so that she would stop screaming, continuing shaking Lucia back and forth,” he wrote.

At the end of the statement, Gibson admits that he may have overreacted.

“While I do not believe I handled the situation as well as I should have, I was worried about the rough way Oksana was shaking and tossing Lucia around, concerned about injury to our then two-month old daughter,” Gibson writes.